2.0 Analysis 2.1 Introduction The analysis will consider the pilot's actions on landing, the location of the watercourse, and the risk the watercourse presents during a runway excursion. 2.2 The Landing It is apparent from witness statements and marks on the runway that the pilot lost directional control of the aircraft shortly after touchdown, and that he was then unable to prevent the aircraft from running off the runway and into the creek. The evidence is consistent with the aircraft either porpoising or wheelbarrowing on landing, but there is insufficient evidence to determine the exact mechanism by which control was lost. 2.3 Injury and Damage The creek was the only obstacle in the path of the aircraft as it ran off the runway. Except for the collision with this obstacle, it is probable that the pilot would have been uninjured and the aircraft relatively undamaged. Had the pilot been wearing a shoulder harness, the injuries he did suffer would have been less severe. 2.4 The Watercourse TP 312, Aerodrome Standards, among other things, defines the strip widths required for instrument and non-instrument runways. The Chilliwack runway meets the current requirements (dated 01 March 1993) in that the watercourse lies immediately outside the defined graded area, within the confines of the strip. It also met the requirements of the edition of TP 312 in effect at the time (dated 06 February 1986). However, a drainage ditch lying just outside the graded area, oriented parallel to the strip, is currently required to be contoured and to have a side slope of 4 units of horizontal measures to 1 unit of vertical measure. The standard in effect at the time recommended this same slope but permitted a maximum slope of 3 units of horizontal measure to 1 unit of vertical measure. This watercourse meets neither the 1986 nor the 1993 slope standards for drainage ditches. However, it is TC's opinion that it is a creek or a watercourse and not a drainage ditch. TC has, therefore, concluded that it need not meet the TP 312 slope standards for drainage ditches. It is clear that a ditch, creek or natural watercourse, running perpendicular to the runway poses more of a hazard to aircraft exiting the runway than does one that runs parallel to it. The location of the Chilliwack watercourse, about 1,200 feet from the threshold of runway 24, places it in the path of aircraft departing the runway during the critical take-off and landing phases. Any aircraft departing the runway as the accident aircraft did would likely collide with the bank on the opposite slope, regardless of whether the slope were 1:3 or 1:4. Moreover, since there have been two occurrences of this nature in three years, it is clear that a real hazard exists. 3.0 Conclusions 3.1 Findings The pilot was qualified on the aircraft type. The aircraft was serviced and maintained in accordance with existing directives. The aircraft was not equipped with a shoulder harness, nor was one required by regulation. The weight and centre of gravity were within the prescribed limits. The pilot lost control of the aircraft on landing. There was no evidence of a malfunction that would cause the aircraft to veer on landing. TP 312 requires a 75-foot graded area for Category 2 runways. Because the watercourse begins 77.5 feet from the runway centre line, it is not subject to the graded area requirements. TP 312 requires that, where drainage ditches are located at the edge of the graded area, they shall be contoured in order to reduce structural damage in the event an aeroplane overruns the runway. TC has determined that the Chilliwack watercourse need not conform to the TP 312 standard for drainage ditches because the watercourse is a naturally occurring creek. TC considers the creek to be a naturally occurring watercourse, and, as such, it does not contravene TP 312 Category 2 runway certification criteria. TP 312, Aerodrome Standards and Recommended Practices, fails to address the hazard presented by the uncovered portion of the watercourse located within the boundary of the strip. 3.2 Causes The pilot lost control of the aircraft on landing; the reason for the loss of control could not be determined. The severity of the pilot's injuries and the damage to the aircraft were attributed to the aircraft's collision with the bank of the creek.Contributing to the accident was the hazard presented by the uncovered watercourse's orientation to the runway, its presence within the boundary of the strip, and its proximity to the threshold of runway 24. 4.0 Safety Action 4.1 Action Taken A TSB Aviation Safety Advisory was sent to Transport Canada (TC) in August 1993, indicating that TC might wish to review the adequacy of the Chilliwack Airport in meeting the certification criteria regarding drainage ditches contained in TP 312. TC responded that Both the regional TC officials and the airport operator are aware of the risk that this watercourse represents but it remains the responsibility of the airport operator to take action to remove this hazard. In November 1994, a supplemental Advisory was sent to the operators of the airport, the District of Chilliwack. This Advisory indicated that, given the bank condition of the drainage ditch, an excursion off the runway by an aircraft, even though remaining within the theoretical confines of the runway strip, could result in serious injury or damage. Therefore, the District may wish to consider contouring the drainage ditches located at the edge of the Chilliwack Airport graded area.